Turbine blade



March 25, 1941. P, FAB R 2,236,426

TURBINE BLADE Filed July 21, 1959 Patented Mar. 1941 PATENT omcetiengesellschaft Brown Switzerland Boverl & Cie, Baden,

Application Jilly 21, 1939, Serial No. 285,822

In Germany July27, 1938 7 Claims. ((1 60-41) This invention relates toturbine blades and particularly to gas turbine blades of the type inwhich a stream of a cooling fluid, such as cool air, flows over thesurface of the blade as aprotection against overheating by the hotgases.

Hollow blades with outlet openings along the center of the leading edgeof the blade have been used but this location of the outlet opening orslit has the disadvantage that the slit may be clogged by dust, cindersor other foreign matter in the high temperature gas. According toanother prior design, the outlet slit or slits have been at the sides ofa hollow blade, but the thin blades r and blade parts were eroded in ashort time by the unavoidable impurities in the gas.

An object of the present invention is to provid gas turbine bladeshaving a main section and a leading edge or fore section to which acooling fluid is supplied, the-passage for the cooling fluid and theopenings for discharging the fluid at the blade surface being in thefore section or, alternatively, between the main and fore section of theblade. An object is to provide a blade having a main section and a foresection that is of harder metal than the main section, there being anair passage and outlet slits in the fore section or between the foresection and the main section. An object is to provide a turbine bladehaving a main section and a fore section, of crescent shape incross-section, that serves as the leading edge of the blade and isspaced from the main section to form an air passage and outlet slitsbetween the main section and the fore section.

These and other objects and advantages of the invention will be apparentfrom the following specification when taken with the accompanyingdrawing in which:

Fig. 1 is a transverse section through a turbine 4 blade embodying theinvention;

Figs. 2, 3 and 4 are fragmentary elevational views, with parts in.section, of different forms of multl-part blades and mountingstherefor;

Fig. 5 is a transverse section through another 45 form of blade;-

Fig. 6 is a transverse section through the root of the fore section ofthe blade shown in Fig. 5; and

Fig. 7 is a transverse section through another embodiment in which theair p sage is formed, in part, by a longitudinal groove in the main section of the blade.

As shown in Figs. 1 to 4, the turbine blade is formed by a solid mainsection I and a fore section 2 that is of approximately crescent shapethat constitutes the leading edge of the blade. The curvatures of theadjacent longitudinal surfaces of the two blade sections are such that apassage 3 is formed between the sections and outlet slits l are providedalong each side of the blade.

Cooling fluid that is supplied to the passage 3 will flow out throughthe slits l, as indicated by the lines a, to protect the main section ofthe blade from the hot gas that travels along the path indicated by thebroken lines b. The main section may be formed from the materialscustomarily employed but the fore section 2 is preferably formed of aparticularly hard metal, such as Stellite," chrome-nickel-tungsten steelor the like that can resist erosion by the dust and cinders in the gas.The composite blade may be either a moving blade or a stationary guideblade. I

The main section! is provided with the usual pressedor milled projectingbase 5 for engagement by the flanged parts 6 that mount the blades inthe undercut groove of a blade carrier 1. The fore section 2 must bemounted in such manner that the cooling fluid may be supplied to theypassage 3 in the blade from a channel 8 As shown in Fig. 2, the v in theblade carrier. fore section 2 is of the same cross-section throughoutits length and is coextensive with the main section I and its mountingflange 5. Section 2 is secured to the main section I by longitudinalwelds 9 that close the slits 4 at the part of the blade that lies withinthe blade groove, and by weld metal it that forms an ex tension of thecover I! that is welded across the outer end of the passage 3.

As shown in Fig. 3, the fore section 2' is provided with an end flangeI2 which is engaged by the flanged parts 6 that lie between adjacentblades. The construction in other respects is like that shown in Fig. 2.As shown in Fig. 4, the base flanges may be omitted from both the mainsection I, and the fore section 2 of the blade, and each section securedto the mounting pieces 6 by weld metal l3.

The air passage and outlet slits may be formed entirely within the foresection 2a, Fig. 5, that has outer and inner curved walls ll, l5 thatare joined by a longitudinal rib IS. The rib l6 terminates at the ringgroove of the blade carrier and the inner end of the fore section istubular, see Fig. 6. The section 2a is well cooled by the air flow andby the transfer of heat through rib l6 and the inner wall l5 to the mainsection I of the blade. The inner surface of the wall portion I!conforms to the outer surface of the main section I and the parts may bebrazed or welded to each other.

When air passages of large size are required, the wall thickness of thefore section 2 may be reduced, Fig. '7, and a longitudinal groove llformed in the forward edge of the main section la. This construction hasthe advantage of low cost as the erosion-resistant metal of the foresection is quite expensive and it would not be economical to enlarge thefore section to provide a large air passage.

It is to be understood that the invention is not restricted to theparticular constructions herein shown and described as changes may bemade in the design, shape and relation of the parts without departingfrom the spirit of my invention as set forth in the following claims.

I claim:

1. In a turbine blade construction for high temperature gas turbines, ablade comprising a main section and a fore section in advance of themain section and constituting the leading edge of the blade, a bladecarrier having a groove for receiving blades and a channel for coolingfluid opening into said groove, a passage extending longitudinally ofsaid fore section and open through a longitudinal slit to one side ofthe blade, means mounting the inner ends of said blade sections in thegroove of said blade carrier with the passage of said fore section indirect communication with the channel of said blade carrier.

2. In a turbine blade construction, the invention as claimed in claim 1,wherein said fore section is of an erosion-resisting metal.

3. In a turbine blade construction, a blade comprising a solid mainsection and a fore section of approximately crescent shape in transversecross-section, means securing said sections to and spaced from eachother to provide a longitudinal slot along each side of the blade and alongitudinal passage between the blade sections, and means closing theouter end of said passage, whereby a flow of'cooling fluid may beestablished along the surface of the main section of the blade when saidblade is mounted on a blade carrier having a channel therein forsupplying cooling iluid to the blade passage.

4. In a turbine blade construction, the invention as claimed in claim 3,wherein said securing \means comprises weld metal filling said slots atthat portion of the blade which is to be seated within the blade grooveof a blade carrier.

5. In a turbine blade construction, the invention as claimed in claim 3,wherein said securing means comprises mounting parts mechanicallysecured to the inner ends of said blade sections at the outercircumference thereof, said mounting parts serving to secure the bladeto a blade carrier.

6. In a turbine blade construction, the invention as claimed in claim 3wherein the forward edge of the main section of the blade islongitudinally grooved.

7. A turbine blade comprising a main section and a hollow fore section,said tore section having an inner and an outer curved wall whoselongitudinal edges are spaced apart to form a longitudinal slot at eachside of the blade, a rib extending longitudinally of and joining saidwalls, and cover means joining the outer ends of said walls, the innersurface of the inner wall conforming to and secured to the forwardsurface of the main section of the blade, and the inner end of the foresection being tubular and open to the spaces between theinner and outerwalls at opposite sides of the longitudinal rib for supplying coolingfluid to said spaces for discharge through said longitudinal slots.

PAUL FABER.

